This book constitutes the thoroughyl refereed post-proceedings of the 6th International Workshop on Information Hiding, IH 2004, held in Toronto, Canada in August 2004.

The 25 revised full papers presented were carefully selected during two rounds of reviewing and revision from 70 papers submitted. The papers are organized in topical sections on digital media watermarking, steganalysis, forensic applications, steganography, software watermarking, security and privacy, anonymity, and data hiding in unusual content.